Debugging yaw problems (newbie question)

Hi there.
My quad is yawing immediately at takeoff. I’ve just built it and am new to APM. Just wondering how you go about debugging something like this? Is there a log that shows outputs of ESCs or rotation speeds of each motor… or some other QA/analysis method? If you could point me to debugging methods/logs in general, that’d be awesome.

thx

check you prop rotations

You need to post a flight log from the APM to give us something to go on.
See the Wiki here

thanks for links to logging docs. have been going through those. little overwhelming, but super interesting. on the summary, it looks like one motor is a bit slower than the others. is that enough to cause yaw? assuming the solution is esc recalibration or replace esc/motor?

logs here:

log

One prop fell off during a flight. Put back on and tightened real good… seems to have solved the Yaw problem. But still curious about how to interpret the motor output averages. At what point does it move from “WARN” to something else?